Noninvasive quantification of axon radii using diffusion MRI

Veraart, Jelle, Nunes, Daniel, Rudrapatna, Umesh, Fieremans, Els, Jones, Derek K. ORCID: https://orcid.org/0000-0003-4409-8049, Novikov, Dmitry S. and Shemesh, Noam 2020. Noninvasive quantification of axon radii using diffusion MRI. eLife 9 , e49855. 10.7554/eLife.49855

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Abstract

Axon caliber plays a crucial role in determining conduction velocity and, consequently, in the timing and synchronization of neural activation. Noninvasive measurement of axon radii could have significant impact on the understanding of healthy and diseased neural processes. Until now, accurate axon radius mapping has eluded in vivo neuroimaging, mainly due to a lack of sensitivity of the MRI signal to micron-sized axons. Here, we show how – when confounding factors such as extra-axonal water and axonal orientation dispersion are eliminated – heavily diffusion-weighted MRI signals become sensitive to axon radii. However, diffusion MRI is only capable of estimating a single metric, the effective radius, representing the entire axon radius distribution within a voxel that emphasizes the larger axons. Our findings, both in rodents and humans, enable noninvasive mapping of critical information on axon radii, as well as resolve the long-standing debate on whether axon radii can be quantified.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Psychology Cardiff University Brain Research Imaging Centre (CUBRIC)
Additional Information:	This article is distributed under the terms of the Creative Commons Attribution License.
Publisher:	eLife Sciences Publications
ISSN:	2050-084X
Date of First Compliant Deposit:	24 February 2020
Date of Acceptance:	7 January 2020
Last Modified:	04 May 2023 18:01
URI:	https://orca.cardiff.ac.uk/id/eprint/129928

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